Harry Potter and the World's End
by Heir-Emerald
Summary: Harry Potter knew that he was special, but he didn't know just how special he was. A Dark Lord chasing him, giant humans that like eating people invading eastern Europe, Gods and supernatural beings that are all over the place. Harry Potter/Attack on Titan/HighSchool DxD, elements from Percy Jackson crossover. Harry/Harem Smart!Harry Powerful!Harry MoD!Harry UnorthodoxMagic!Harry.
1. Prologue

_**Hi guys,**_

 _ **Quick note of some changes. Harry has crimson black hair instead of raven black hair. This is set approximately 20 years later and this IS a crossover of Harry Potter, Attack on Titan, HighSchool DxD and some elements are implemented from Percy Jackson. Also, Harry is 3 years older than Ron and Hermione, so yea they're born in 2002/03 not 2000. Don't hate over that.**_

 _ **Besides that, enjoy and let me know what you think and if I should continue it :)**_

 _ **Disclaimer! I don not own Harry Potter, Attack on Titan, HighSchool DxD and Percy Jackson.**_

* * *

 _ **Prologue**_

 **31** **st** **July, 2000**

 **St. Mungos' Hospital**

Soft cries echoed through the hospital room silencing the adults comforting the mother in labour. Lily Potter gasped as she saw the nurse wrap her newly born baby in a blanket. Her baby. This was hers and James' baby. Tears pooled her eyes as the nurse gently handed her the baby. Taking a shaky breath, Lily got her first proper look at the newborn. A small tuft of crimson black hair, a natural light tan, her nose, James' high cheekbones. The tan her baby sported confused her. Neither of them had natural tans, so how does her child have it? Lily shrugged it off and softly cooed at the slumbering newborn.

A hand laid itself on Lily's shoulder, turning her to look at her husband. James Potter gave his wife a soft smile and kissed her on the cheek. "This is our son." He whispered.

Lily nodded, tears of joy now leaking from her eyes. "Yes, our son. We need a name for him."

James furrowed his brows in thought. "What about Lachlan?"

"No."

"Jack?"

"Nah-ah."

"James Jr?" The elder Potter joked with a playful grin marring his features.

Lily rolled her eyes at her husband's childishness. _Some things will never change._ The red-head thought.

"What about Hadrian?"

Lily paused. Hadrian? Not a common name and sounds quite noble. "Hadrian sounds perfect." The Lady Potter smiled, kissing her son on his delicate forehead. "Hadrian _James_ Potter." Lily decided.

James gave Lily a face akin to a deer looking at headlights. "Hadrian _James_ Potter?"

"Yes." Lily firmly said. "Hadrian James Potter. We'll call him Harry for short."

James chuckled. "Alright. Hadrian James Potter or Harry James Potter for short then. I suppose that I can name Sirius as little Harry's Godfather?"

"I suppose we can." Lily said with false sadness.

The hazel eyed man gave Lily a dirty look. "Don't be like that now, dear."

Lily giggled. "I was joking, James. Sirius can be Harry's Godfather, as long as I can name Alice as his Godmother then."

"Deal." James said quickly, he wasn't going to try and negotiate any further.

Lily smiled turning her attention back to Harry. "You're my little boy." The red head cooed, hugging him closer to her bosom. James watched over Lily's shoulder, seeing his son began to open his eyes. Both parents grinned as his eyes opened to the world for the first time and gasped.

"Lily." James began. "He's got your eyes."

Sparkling emerald eyes shone with curiosity as Harry saw his parents for the first time. He blinked. Once. Twice. A third time. The he went back to sleep nuzzling into his mother's warmth. He could look at things another time.

* * *

 **7:21am**

 **31** **st** **October, 2002**

 **Godric's Hollow**

Two year old Harry Potter giggled as his Godfather threw him up in the air. He also loved being in the air but for some reason it felt like he didn't belong there. It didn't stop the young Potter from enjoying it though.

"Sirius! Be careful with him will you?" Lily called from the kitchen.

"Don't worry, Lily-flower. Prongslet is perfectly safe with me." Sirius tried to reassure her.

Lily scowled with annoyance. "Must I remind you of the time you thought that leaving him on his own in the backyard was a good idea?"

The Lord Black whimpered. Lily Potter was famous for her temper and protective nature. "That was one time!" He argued.

"Didn't stop Harry from going missing on us for almost four hours before we found him sitting on top of the roof somehow."

Sirius shrugged. "Accidental magic."

"What are we talking about?" James yawned, walking down the stairs.

"Sirius is throwing Harry around"

Raising a brow, James turned to look at the grim animagus, "Wait until Harry gets to ride his broomstick again." James shared a laugh with Sirius with the giggling Harry now squirming in his arms.

"NO! That will _not_ happen again!" Lily said storming up to Sirius, taking her son from his arms.

"Come on Lily-flower." James tried assuring. "Nothing went wrong last time."

"I almost got hit by him going full speed while you, Sirius, Remus and Peter was laughing your arses off!" Lily retorted.

James and Sirius cringed and recoiled at Lily's tone. "But he didn't fall off, Lily. He's a natural. Like a true Potter." James said with a faux cry.

Lily started bouncing Harry on her hip, cooing at him. "He isn't going to start riding brooms until he turns eight, James."

James whimpered and sat down at the breakfast table as Lily strapped Harry into his highchair. Sirius sighed, joining his best friend and Godson while waiting for Lily to finish making breakfast. "Where's Moony and Wormtail?" James asked, flipping open the Daily Prophet.

"Well Moony is doing his mission for Dumbledore and I have no idea where Wormtail is."

"Wormtail's been disappearing quite a bit lately, hasn't he?"

"Yeah…" Sirius said, a troubled look coming over his face. "Maybe he's just been feeling sick?"

"I hope it's just that…" James agreed.

"Stop being such a Debby downer, you two." Lily said placing their plates on the table and sitting down next to Harry, with his breakfast in hand. "Besides, they know how to take care of themselves. They aren't some silly first years pulling pranks at Christmas feasts aren't they?"

Both men gave the red head a sheepish look and scratched the back of their heads. "Of course not." They replied simultaneously.

Lily rolled her eyes and mumbled "At least not anymore they aren't."

The adults fell into a comfortable silence only being broken by Harry's cooing and squealing.

"Come on, Harry, we can play after you finish your breakfast." Lily whispered, smiling at her son's adorable grin.

Harry cooed, trying to swat the spoon out of the air. Lily giggled, managing to avoid his swinging and give him a spoonful of his breakfast.

Standing up, James groaned as he stretched. Hearing a pop he sighed in satisfaction and discarded his plate in the kitchen sink. "Well, love, Padfoot and I have got to go to work, I'll see you when I get home."

The Lord Black groaned as he placed his plate in the sink. "Sometimes I wonder why we became Aurors with this stupid waking up early and staying out late stuff."

"It's because you have, what is it that you said? Oh yes I remember now, 'a sense of adventure'." Lily mocked as she cleaned Harry's mouth with his bib.

"Anyway," James intercepted, sensing an argument about to break out. "We should get to work, Padfoot. Our shift starts in 30 minutes."

"Yeah, yeah…"

The Lord Potter leaned over capturing his wife's lips in a passionate kiss, "I'll see you when I get home." James turned his attention to his son, lifting him out of his high chair and nuzzled his son's stomach earing a giggle from him, "I'll see you later, little man."

Harry chortled, wrapping his arms around his father's head, "See wou waiter, daddy."

James grinned and handed Harry back to Lily, "Come on, Padfoot, we have some Death Eaters to catch." With that, James Potter stormed from the house, determination written on his face.

* * *

 **11:08pm**

 **31** **st** **October, 2002**

 **Godric's Hollow**

Silent footsteps crept up to the front door of the Potter's residence, with a smirk on his face he placed a silencing charm on the front door to prevent the slumbering Potters from hearing the door creak open, "Alohamora…" The man whispered, a dark smile creeping onto his lips as the door unlocked. _One would think with that Mudblood having a mastery in Charms that she would place some strong charms on the door to be safe. Stupid blind faith in that old man, I would say._ The man thought as he placed another set of silencing charms on his feet.

The robed man softly slid up the stairs, like a snake to a tree. He crept towards the master bedroom where Lily and James Potter were resting, a cruel smile curled unto his lips as he waved his wand, locking the bedroom door and sending silencing charms at the door and walls. _This is almost too easy. I have only needed to use silencing charms, locking charms and an unlocking charm._ The man glanced at the door again. _You shouldn't trust your friends, Potter. Because you will never know when they stab you in the back until it's too late._

The man kept moving down the hallway, seeing a soft glow coming from the last bedroom on the left. He opened the door, careful of making much noise and peeked at the crib in the corner of the room. The robed man stepped up to the crib, removing his hood. Pale, white skin, red eyes that resembled the colour of blood, dark hair that was starting to grey from age, high cheekbones resembling someone from a noble family.

 **The one with the power to vanquish the Dark Lord approaches…**

 **Born to those who have thrice defied him, born as the seventh month dies…**

The words of the prophecy echoed through his mind as he delicately gripped his wand. Yew 13¼ inches, phoenix tail feather. The blood eyed man caressed the wand, as if it were a newborn baby and he was its father. The man turned the wand at the baby. "So you are the one who is to defeat me…?" The man all but whispered. "No one can match the power of Lord Voldemort." The Dark Lord almost growled, the thought of someone matching his power infuriated him.

Emerald eyes fluttered open, to see a robed man with a wand trained on him. What was this strange man going to do? Harry Potter didn't know but he felt uncomfortable and started fidgeting and waved his arms around.

The Dark Lord stared at Harry's emerald eyes. _Such beautiful eyes…_ Lord Voldemort thought as raised his wand aiming it at the boy's forehead. "I'm sorry, little one but I can ** _not_** take any chances of someone defeating me. I am doing what is best for the magical world…" Voldemort whispered. The Dark Lord didn't notice the soft green glow coming from the back of Harry's hand.

 **"Avada Kedavra."**

The green killing curse left the Dark Lord's wand hitting Harry Potter's forehead. The glow on the toddler's hand glowed dangerously, and a roar was heard. As soon as Lord Voldemort heard the roar, he recognised instantly that it was the cry of a dragon. _But where did..?_ Voldemort eyes widened as the killing curse he sent at the boy, grew a dangerous, dark green and was sent back at the Dark Lord. The Dark Lord screamed in agony as his soul was ripped from his body, dispelling him into a spirit.

Harry Potter stopped moving in his crib, a lightning bolt shaped scar glowed on his forehead where the Dark Lord hit him. The young Potter's hand had also stopped glowing as the dragon's roar stopped.

It would be found by Lily and James Potter the next morning, the robes and wand of the Dark Lord and the strange lightning bolt scar upon their son's forehead. Yet, neither of Harry's parents would know about the dragon's cry or the green glow from the back of his hand…

* * *

 _ **Well there's the Prologue.**_

 _ **Let me know if you want me to continue it or not. I've had this idea for a while and just felt like I should write it up :)**_

 _ **Thanks, PercyK**_


	2. Chapter 1

**Alright, lads and lasses.**

 **I'm quite happy with the responses I got from the Prologue so thanks guys.**

 **Now, 1stHorseman has asked me who is in the Harem. Well I could tell you or I could make you guess... hmm I like the sound of you guys guessing so leave a review and let me know who YOU think will be in it :p**

 **Quick note about the Harem. Hermione and Ginny are NOT in it, so sorry to everyone who were hoping they were... BUT I will say that there will be seven girls. Yes people, SEVEN girls, so have fun guessing who.**

 **ANOTHER IMPORTANT NOTE: Levi and Issei do NOT exist in this story... you'll see why ;)**

 **Here is Chapter 1 and I hope you guys like it :)**

 **I do not own Harry Potter, Attack on Titan, HighSchool DxD and Percy Jackson.**

* * *

 **4** **th** **November, 2002**

 **Headmaster's Office, Hogwarts**

Three years had passed since the disappearance of Lord Voldemort. The wizarding world rejoiced as the most powerful Dark Lord in recent times was perished by the young two year old Harry Potter who was prevailed and named the Boy-Who-Lived. Harry would become an icon in the wizarding world and was admired by all magical humans, both old and young.

All believed in the death of Lord Voldemort but one person. Albus Dumbledore still had his own suspicions that the Dark Lord was still alive but in a weak state. How? The Hogwarts Headmaster didn't know but he didn't believe what the wizarding world had thought. The Headmaster suspected that Voldemort dabbled so far into the dark arts that he was able to sustain a consciousness. The lightning bolt scar on the young Potter heir's forehead supported his theory, but if he could just get a clue of how the Dark Lord managed to…

The old Headmaster took his half-moon spectacles off and rubbed the bridge of his nose, _Tom Marvolo Riddle…_ Dumbledore thought. _There is no way that you have perished. The magical residue that resided in Harry's room should not be that powerful. Death doesn't leave a magical signature like that. Another mystery to me is how young Harry survived a direct hit from the killing curse. It should not be possible… shouldn't it?_ The defeater of Grindelwald pondered over his thoughts, trying to pick out anything that could have happened but all he could do is furrow his brows in frustration. _Maybe Severus will have an idea…_

* * *

 **9:39am**

 **17** **th** **December, 2005**

 **Potter Manor**

Harry Potter sat in the family library reading through a book on basic Charms. He decided to read on Charms because he heard from his father and mother that something like Transfiguration or Potions was too complex to start reading for a five year old, so he decided that maybe Charms would be a good place to start. The Boy-Who-Lived didn't start reading through his family's library because of expectations on him from his parents or the wizarding world, but rather because he wants to be better than his parents, grandparents and Albus Dumbledore. He wanted to make a difference in the world like they have.

His father is an Auror and has a mastery in Transfiguration, his mother had a mastery in Charms and Potions, his grandfather and grandmother are distinguished members of the Wizengamot and Albus Dumbledore had a legacy that is rivalled by no one. The old man was the Headmaster of Hogwarts, the man who defeated the Dark Lord Gellert Grindelwald, Chief Warlock of the Wizengamot, Supreme Mugwump of the International Confederation of Wizards and the only man Voldemort was unnerved by. So Harry had a **_lot_** to live up to.

Harry flipped to the next page in his text to start reading on the Levitating Charm when he heard his mother call for him. Sighing, the Potter heir placed his bookmark in the book and made his way towards the living room. He was greeted by the sight of his mother struggling to keep his younger sisters from destroying any of the delicate trinkets on the shelves in the corner of the room. Harry knew why his mother just didn't use magic to stop them. She didn't want to take the chance of hurting his sisters, thus making his mother do it the muggle way.

"Harry, dear, could you please get Violet and take her to the couch." His mother asked as she picked up his younger twin sisters, Kathrine and Savannah.

Harry picked up Violet and placed her on the couch with his other sisters. Violet was a year old, being born on the 5th April, 2004, while Katherine and Savannah are twins and are about ten months old being born on the 19th February earlier in the year. Now one may question how ten month old babies can move around on their own? Well Harry was told by his grandmother that babies that had magic develops quicker than a non-magical baby due to the magic in the child growing at a rapid pace to sustain a healthy body in case of spurts of accidental magic.

* * *

Lily Potter breathed deeply as watched her four children. The aftermath of Voldemort attacking their home in Godric's Hollow had scared herself and James. What was worse was that the Dark Lord managed to walk into their home so easily and make sure that James or she didn't hear what he attempted to do to Harry. It still sent nerves down her spine. When she found Harry in his crib the next morning, she screamed bloody murder at the state of the room, the robes and wand of the Dark Lord and finally the state her baby boy was in. He wasn't moving and looked like he was actually dead if it weren't for the fact that she could see his torso softly moving up and down. James had immediately left to contact Albus and Sirius while she picked up her son, tears streaming down her face praying to any deity that her baby was alright.

Lily had looked at Harry closely, noticing a scar on his forehead resembling a bolt of lightning. It look red and irritated, making Lily sob more. James stormed into the room Sirius and Albus in tow. Albus immediately walking over to Lily and Harry to get a look of him. The Hogwarts Headmaster then turned his direction to the robes and wand in a heap on the floor. Albus withdrew his wand and waved it, scanning the room, brows furrowing when he got the results. Looking at Harry again, Dumbledore ran Diagnostic Charms over his head and had told her that Harry was fine but just exhausted. Not magically but physically. She remembered breathing a sigh of relief over that, cuddling her son closer to her bosom.

James and Sirius had turned around facing herself, Harry and Albus, anger written across their faces. She had given him a questioning look and all she got from him as an answer was "Pettigrew" and apparated out with Sirius to the Ministry of Magic.

All that she remembered after that was Sirius getting arrested by the Aurors after finding Peter Pettigrew, and sending a Curse at a nearby gas tank, killing thirteen muggles and Peter Pettigrew himself. It was lucky that James bailed him out after Sirius took Veritaserum and James confirmed that Peter was their Secret Keeper instead over Sirius. It was also revealed that it was Peter that sent the Curse at the gas tank instead of Sirius, which was lucky for him to not get sent to Azkaban for goodness knows how long.

* * *

While Lily was lost in her own memories of what happened three years earlier, Harry had left back to the library to continue reading his text on basic Charms. Harry weaved through the corridors of Potter Manor and walked back into the family library, picking up the text flipping back to the page he was on.

 _The Levitation Charm, also known as the Hover Charm, Rocket Charm or the Floating Charm was created by Jarleth Hobart in 1544. The Charm, as what is assumed, is used to levitate objects and move them in a much easier way._

 _Hobart created this Charm, believing that he had made a way for wizards to fly without any assistance. Hobart exposed the Charm to the public, but believed that his clothes were weighing him down, thus stripping his clothes to make him naked. What Hobart had not taken into account is that to use the spell, you need not only intent but a powerful magical core to not only, lift himself in the air, but keep himself stabilised and not lose his concentration. Thus, he fell out of the sky and broke sixteen bones._

 _To practice this spell, the wand movement is a simple, "swish and flick" of the wand and the incarnation is, "Wingardium Leviosa." Pronounced, '_ _wing-GAR-dee-um levi-O-sa'. Note: Be careful of what object to practice with for the first time._

Harry closed his eyes in thought, could the Charm be done wandlessly? The Potter heir didn't know but he would give it a shot. Closing the book, Harry curled his hand closed so that his index finger was pointing at the book "Wingardium Leviosa." Harry whispered carefully, with the swish and flick movement with his finger. The Charms book, appeared to shake on the table then stop. Narrowing his eyes, Harry tried again. "Wingardium Leviosa." The book shook a moment or two longer than before then stopped. _Intent_ Harry thought. His intent was to lift this book. Taking a breath, Harry tried a third time, "Wingardium Leviosa." The book shook more furiously on the table, yet slowly, started to lift off the table. One inch. Two inches. Three inches. The book wobbled and Harry grunted under the strain. With a 'thud' the book dropped back onto the desk.

Harry smirked victoriously, whilst wiping the beads of sweat off his forehead with the sleeve of his sweater. He did it! He actually managed to lift the book. Without a wand too! Harry left the book on the table. The cleaning House Elves knew that he didn't like having the books he was currently reading placed back onto the shelves. Walking back into the living room, Harry glanced at the grandfather clock in the corner of the room. _1:27? Have I really been in the library that long?_ Harry thought to himself. With a shrug, he decided maybe he would go for a swim.

* * *

After getting changed into his board shorts, Harry walked out to the back of the manor to the pool. Harry knew he was a responsible child that is why he didn't get his mother to come with him to the pool, she trusted him as well, so that helped. Can't say the same about flying on a broom though. Go figure. Harry slipped into the cold water, a sigh came from his lips as he did so. He loved swimming. He felt like he was home whenever he was in it. Especially when his parents took him to the beach a couple years ago. He felt like he actually was home when he was in the ocean. Harry didn't question why, he just took comfort that he could be somewhere that outside of the library or his room that felt great.

Harry paddled in the water for the next hour, laughing as he splashed water around.

 _"Hadian…"_

The young Potter stopped moving. Who was calling his name? He waited for a minute before shrugging and kept splashing about.

 _"Hadrian…"_

 _Okay._ Harry thought. _There is no coincidence that someone called my name twice and it wasn't mum because she's dealing with Violet, Katherine and Savannah and dad's still at work… so who?_

 _"Hadian James Potter."_

Harry jumped in surprise turning around in the water, eyes as big as the moon.

" _Harry."_

The Potter heir's eyes got impossibly larger when a man appeared from nowhere in a gust of mist. "Who are you?" Harry gasped out, a sliver of fear shaking through his body.

The man appeared to be about 6'1", windblown jet black hair, suspiciously similar to his own. A neatly trimmed beard, yet had that slight roguish look to it. Tanned skin which indicates that the man had spent a lot of time outdoors, sparkling eyes that resemble the sea. Harry felt comfort and safe looking at them, which made Harry more nervous. The man wore a Hawaiian patterned button up shirt, khaki Bermuda shorts and flip flops on his feet. A soft smile had made its way onto the tanned man's face.

"Hello Hadrian." He said with affection.

"Wh-Who are..?" Harry stuttered, stumbling over his words.

The man chuckled, "No need to be nervous around me, Hadrian."

Harry opened his mouth to speak, wanting to ask the man again who he was again, but the man shushed him.

"Hadrian… Harry. It's nice that I can finally meet you, physically at least, for the first time."

"Wait! What is that supposed to mean?"

The man chuckled, tapping his temple with a knowing smile, "I've been watching you since you were born, Harry."

"You've been watching- wait just who are you?" Harry said, defiance now laced in his eyes.

"You really are my son."

"…What?" Harry questioned, mind buzzing from the confusion the man was causing.

"Harry… my name is Poseidon, and well, I am your father." Poseidon said.

Harry jaw dropped in shock. No… No it can't be. James Potter is my father... isn't he? Harry couldn't stop himself as he blacked out from shock.

* * *

 **Okay so there is Chapter 1.**

 **I'm surprised I manged to do it this quickly... heh**

 **Anyway, till next time.**

 **\- PercyK**


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